Deodorized polymers of C.sub.4 olefins with excellent humectant properties demonstrate an improved storage and color stability at temperatures of up to 200.degree. F. for extended periods. These polymers are prepared by polymerizing isobutylene or a mixture of C.sub.4 hydrocarbon olefins containing at least two of isobutylene, 1-butene, 2-butene and butadiene in the presence of a catalyst, at a temperature within the range of from about 100.degree. F. to about 140.degree. F. to obtain a polyisobutylene of from about 100 to 4000 molecular weight. Another method is by stripping or by taking an overhead cut from a heavier grade of polyisobutylene to obtain a fraction of a molecular weight of from about 100 to about 4000. The polymerization product is hydrogenated and deodorized by nitrogen stripping to remove at least 2 (wt) % of the hydrogenated product and by contacting the stripped product with attapulgite clay in a ratio of 1:1 to 10:1. The deodorized C.sub.4 polymers of a molecular weight range of from about 100 to about 4000 have excellent humectant properties and are desirable for use in dermatological preparations. The molecular weight range assures compatibility with many components of these preparations.
Dermatological preparations relating to treatment for irritated, pruritic and dry skin conditions have as a general objective the controlling or retarding of the degenerative or chemical breakdown of the skin sebum, lipids, protein, exudates or surface films so as to provide improved skin protection.
As a topical application, a dermatological preparation cannot have, or develop, offensive odors even though the preparation may contain perfume to add a pleasing fragrance.
Accordingly, this invention relates to deodorized substantially saturated isobutylene polymers of a molecular weight of from about 100 to about 4000, an average molecular weight of about 200 to about 350, a viscosity at 100.degree. F. of 3-37 centistokes, color, haze - 5 APHA max, haze free - 10 APHA max, and bromine index - 1000 max, wherein the isobutylene polymers are substantially free of odor-causing aldehydes, ketones, esters and peroxides and are suitable for replacement of squalane, fatty esters, and other moisturizing agents used in cosmetics.
Squalane, obtained from natural sources, is one of the most common moisturizer agents and is useful as a base oil for cosmetics. However, production is low, the price is high, and quality is not uniform. These problems thus make a squalane substitution desirable.
Purification of lower monoolefin polymers such as polyisobutylene has typically been by means of hydrogenation to produce a saturated compound, as is taught in U.S. Pat. No. 3,100,808 (Dyer), to render the resulting saturated polymer substantially colorless, odorless and stable. Although the hydrogenation process does reduce the odor and color-forming impurities, the hydrogenated polymer contains odor-causing aldehydes, ketones, esters and peroxides which, on storage, further oxidize to objectionable color- and odor-causing compounds.
In the prior art, U.S. Pat. No. 4,061,780 (Yoshida, et al.) teaches purification of isobutylene polymers for use in cosmetic applications wherein a liquid C.sub.4 olefin fraction is polymerized in the presence of a catalyst. The polymerized reaction product is distilled to obtain a fraction having a boiling point range of 120.degree. C. (248.degree. F.) to 200.degree. C. (392.degree. F.) at 1-2 mm Hg to remove compounds having a molecular weight of less than about 250 and compounds having a molecular weight of more than 600. The resulting fraction is hydrogenated and deodorized by steam distillation under reduced pressure or treatment with activated carbon, or solvent extraction or by a combination of steam distillation, treatment with activated carbon and solvent extraction. The initial distillation of the C.sub.4 polymer fraction is taught as removing compounds which can easily oxidize to form odorous compounds.
The procedure taught in the prior art to obtain a purified isobutylene polymer suitable for cosmetic use accordingly is complex, economically costly in required process equipment, and would not be easily adapted to a continuous method in a commercial application.
Accordingly, the instant invented process comprises an improved method for production of purified hydrogenated isobutylene polymer which closely matches the outstanding feel and moisturizing ability of squalane, which does not readily oxidize, contains no cyclic compounds, imparts no taste and does not deteriorate on storage. The invented process can be in batch or continuous mode, is not complex in operation and uses readily available process equipment.